1. Field of the Invention
The present invention relates to a cylindrical member which includes a sleeve, a flange fitted and bonded into the end portion of the sleeve, and a space-controlling member provided at the end portion of the sleeve for controlling the space between the peripheral face of the sleeve and another member. The present invention also relates to a developing roller and a photosensitive drum of an image forming apparatus that employs the above cylindrical member for electrophotography, and further to an electrophotographic apparatus equipped with the developing roller or a photosensitive drum.
2. Related Background Art
Conventionally, a developing roller of a development device of a conventional image-forming apparatus, as shown in FIG. 5, comprises a cylindrical sleeve 12a, and a developing roller flange 12b bonded permanently at the end portion thereof. At the fitting portion, the inside diameter of the sleeve 12a is larger than the outside diameter of the flange 12b, usually by approximately 30 .mu.m, for the purpose of applying a prescribed amount of an adhesive 9 between the sleeve 12a and the flange 12b for bonding them.
The bonding is practiced specifically such that an adhesive 9 is applied uniformly onto the inside peripheral face of the end portion of the sleeve 12a where the flange 12b is fitted, then the flange 12b is inserted thereto, and the adhesive 9 is completely cured at a constant temperature and humidity. Usually, the adhesive includes instantaneous adhesives, and combinations of an adhesion primer and an anaerobic adhesive. The adhesive is selected depending on the required bonding strength for the use and the purpose.
The above constitution of conventional developing rollers has disadvantages shown below.
(1) When the adhesive is applied and completely cured at a high temperature and a high humidity (e.g., at a temperature of 32.5.degree. C., and a relative humidity of 85%), the moisture in the air affects adversely the adhesion during the curing process, causing unstable bonding such as may result in separation of the sleeve and the flange, and slippage between them owing to the deterioration of the adhesion.
(2) Some adhesives require a very long time for complete curing, which necessitates use of a storage space for a long time, and installation for keeping a constant temperature and a constant humidity of the storage environment, and therefore is disadvantageous from the standpoint of cost, management and productivity.
(3) Conventionally, the constitution around the developing roller is as shown in FIG. 2, comprising a magnet roller 14, a developing sleeve 12a, a developing roller flange 12b, a spacer roller 18, a developing roller bearing 16, a developing roller gear 17, a holder 15, a photosensitive drum 1, and a photosensitive drum gear 1b.
In FIG. 2, the flange 12b is inserted into the sleeve 12a with a gap, and is bonded by use of an adhesive. Therein the magnet roller 14 is enclosed. The developing roller is supported at both ends thereof by the bearings 16. The bearing is fixed on the holder 15 by a positioning pin and a hole which are not shown in the drawing. The magnet roller is also fitted to the holder 15. On the other hand, the photosensitive drum comprises the sleeve 1a and the gear 1b which are bonded with an adhesive. The developing roller and the photosensitive drum are pressure-contacted through the spacer roller 18 by aid of a spring 8. The spacer roller keeps constant the distance between the developing roller and the photosensitive drum. The photosensitive drum is rotated by receiving rotational driving force from the main body of an image-forming apparatus through the gear 1b to rotate the developing roller in the direction indicated by the arrow, through the developing roller gear 17.
Therefore, if the sleeve 12a and the developing roller flange 12b are not coaxial and deviate from each other by the distance A as shown in FIG. 5, then the outside diameter of the flange 12b swings with an amplitude of twice the dimension A relative to the outside diameter of the sleeve 12a when the developing roller is rotated through the developing roller gear 17 by the driving action of the photosensitive drum gear 1b. Accordingly, the magnet roller 14 moves by a distance of twice the distance A in one rotation relative to the surface of the photosensitive drum 1. As the result, the magnetic force exerted on the photosensitive drum swings, causing irregularity of image density corresponding to the rotation cycle of the developing roller.